Weapon special ability 'Bane', in particular, Bane vs Evil Outsiders... Does this special power bestow the weapon with the ability to overcome the DR of the foe...? I'd guess that it doesn't, seeing as it would be kinda overpowered... Bane vs Magical Beasts shouldn't overcome the DR on the Tarrasque, for example... I think I just answered my own question...

Also, Arcane Trickster for Divine magic users, is there a Prestige Class or an adaptation out there for a Halfling Cleric(Olidammara)/Rogue with full Spellcasting and Sneak Attack...?

Aaaand, I made a feat, which I'm sure is already out there, but let me know if it seems broken- Extra Breath Prerequisites: Base attack bonus +6, Con 17+, must have a breath weapon usable no more than once per day. Benefit: Creature can use its breath weapon 2 more times per day, for a maximum of 3 breaths per day. The creature must wait 1d4+1 rounds between breaths...

"Bane" adds extra damage when the weapon is used against the creature of its type, but does not bypass DR. However special abilities have to be coupled with an enhancement bonus, so Bane weapons are at leat +1. Therefore a Magical Beast with a DR 10/magic gets no protection from the Bane weapon Gimp uses as an example. Against a Magical Beast with DR 10/cold iron, the Bane damage (2d6 typically) still applies, but 10 points is still shaved off the damage.

No limit per day?!?!? WTF?!?! What are the Prerequisites...? That is most certainly a broken feat... I can't begin to imagine the carnage if one of my players started running around breath-weaponing everything in sight at will...

If you're allowing a character to use such high ECL templates, balance tends to take a backseat anyway ...

Not at will, per se, but at 1d4+1 rounds in between. This is the same as what full-blooded dragons can do (albeit at much less damage potential). There are other means in the book to breath-weapon at 1d4+1 rounds than being a half-dragon, though, so the rules taken together in their entirety don't become as broken.

I made a build that used breath weapon (Dragon Shaman) combined with the Metabreath feats from Dracinomicon and it wasn't the most broken build I've come up with by a longshot, though.

There is the Divine Prankster in Races of Stone, but that is Gnome only. I'm sure you can get a DM to let you play that as a halfling though, since the flavor is about the same (only CN vs. CG and worshipping Olidammara vs. Garl Glittergold).